Fetal blood sampling is extensively employed during birth if a physician suspects that the fetus may be receiving an improper amount of oxygen due, for example, to strangulation by the umbilical cord or premature separation of the placenta. Conventionally such sampling involves inserting an endoscope through the birth canal and pressing it against the fetal presentation. The presenting field is illuminated by a small light which is positioned in a fixed manner on the larger or proximal end of the endoscope. The presenting field or puncture area is cleaned of body fluids by using long swabs which are inserted through the endoscope and a silicone jelly is applied to induce a large drop of blood to form when the skin is punctured.
It should be noted that if the endoscope does not seal properly against the fetal presentation the puncture area will become contaminated by body fluids and the procedure must be started over. Once an uncontaminated field is prepared, the physician then introduces a lancet through the endoscope to make an incision. After the incision is made, the lancet is removed and a long glass capillary tube is advanced to collect the blood sample. The blood is then tested for its PH value which is a function of the amount of oxygen in the blood.
This conventional technique is illustrated in FIGS. 1 and 2. It is well known that there are several dynamically varying geometries during the birth process. The length of the birth canal, the dilation of the cervix, and the angle of the fetal presentation with respect to the birth canal all vary during the birth process. During early stages of birth, the tangent of the fetal presentation lies at a rather substantial angle with respect to the centerline of the birth canal as shown in FIGS. 1 and 2. Making a good seal against the infant's head with the endoscope at this stage of the birth process is extremely difficult. In FIG. 1 a conventional endoscope 10 is shown inserted through vagina 12 until the end of the endoscope is near cervix 14. In order to make a good seal between the oblique angle of the end of endoscope 10 and the infant's head 16, the doctor must stretch vagina 12 in an effort to locate the infant's head 16 through the cervix 14 as shown in FIG. 2. Due to the geometries involved, considerable pain is experienced by the mother during the stretching of the vaginal tissues and it is still difficlut to get a good seal between the end of endoscope 10 and the baby's head 16. Accordingly, the possibility of contamination of the subsequently taken blood sample is greatly increased.
One attempt to deal with the problems noted above is disclosed in U.S. Pat. No. 3,685,509 to Bentall which discloses a blood sampling endoscope having an evacuated tubular end portion for adhering to the fetal presentation. The endoscope includes a custom formed capillary tube, a freely moveable lancet, and a vacuum tube as part of the device. The use of this device has several drawbacks. It introduces a new requirement for additional equipment since suction must be applied to the annulus of the endoscope. The necessity for additional equipment may be both costly and burdensome. The additional wall thickness of the endoscope which contains the evacuated tube may require that the cervix be dialated more than is required with a thinner walled conventional endoscope. The external capillary and suction tubes may add to the difficulty of insertion and interfere with the movement of the endoscope when in position, e.g. when adjustments are made to accommodate movement of the mother or fetus. The fact that the capillary tube is captured in this endoscope limits the movement of the capillary tube thereby making interception with the blood more difficult. The additional length of the endoscope that accommodates the lancet handle and the bent end of the capillary tube requires that the procedure be carried out at a more distant point of vision than would normally be required, especially during the latter stages of the birth process when the fetal presentation is relatively close. As with conventional endoscopes, the distal end of the Bentall device is also terminated at a 90.degree. angle with respect to its longitudinal axis.
The present invention is directed to solving one or more of the problems set forth above.